Electrochemical detection of DNA hybridization based on carbon-nanotubes loaded with CdS tags

An effective method for amplifying electrical detection of DNA hybridization based on carbon-nanotubes (CNT) carrying a large number of CdS particle tracers is described. Such use of CNT amplification platforms is combined with an ultrasensitive stripping-voltammetric detection of the dissolved CdS tags following dual hybridization events of a sandwich assay on a streptavidin modified 96-well microplate. Anchoring of the monolayer-protected quantum dots to the acetone-activated CNT was accomplished via hydrophobic interactions. SEM images indicate that the nanocrystals are attached along the CNT sidewall, with a loading of around 500 particles per CNT. A substantial (500-fold) lowering of the detection limit is obtained compared to conventional single-particle stripping hybridization assays, reflecting the CdS loading on the CNT carrier. A large excess (250-fold) of non-complimentary oligonucleotides have minimal effect on the response. Such use of CNT as carriers for multiple electrochemical tags offers great promise for ultrasensitive detection of other biorecognition events.